Charcoal is mostly pure carbon, made by cooking wood with low oxygen. The process can take days and burns off volatile compounds such as water, methane, hydrogen, and tar, and leaves about 25% of black lumps and powder of the original weight. is an odourless, tasteless, fine black powder, or black porous solid consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances.
The quality of charcoal is defined by various chemical characteristics, although properties are interrelated, but they are measured and appraised separately. Most of the specifications that control charcoal quality have originated in the steel or chemical industry. The moisture content together with the ash content is very important to charcoal’s chemical properties that define its quality. Moisture lowers the calorific or heating value of charcoal. Thus, charcoal fresh from the kiln contains usually less than 1% of moisture, but the moisture content could reach 5-10%, as absorption of moisture from the humidity of the air itself is rapid.
Good quality charcoal typically has an ash content of around 3%, but if material less than 4 mm is screened out the plus 4 mm residue may have an ash content of about 5-10%.